Wondering if anybody has information on this 88H slide? It seems to have a different taper than other 88H slides I've come across. First 2 pics are of the unusual taper and the bottom 2 pics are of a regular 88H slide. Thanks for any info!

Is the tenon taper different (part that goes into the bell section) or is the mouth0iece receiver taper different?

I'm not aware of any changes in the tenon tapers of any 88H (or 8H) trombones over the period they have been made.
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There has been a change in the taper of the mouthpiece receiver. The large bore Conn trombones (8H/88H/Basses) used a B&S Taper (often referred to as a Remington taper) from at least the 1940s until the Gen II 88H. Modern Conn 88H trombones take the standard Morse taper everybody else uses.

Both tenon and mouthpiece. Seems to be a slight taper that I don't normally see on other 88's. I know about the old Remington taper's, but this is an Eastlake horn. Not sure if it was a custom job someone had done, or what.

Your photos are close-ups so have some optical distortion. It looks a bit odd but I really can't say it is not the photo. How about a shot from farther away and with the slide placed flat on a surface?...